The lack of simple, inexpensive and high throughput exposure assessment technologies has limited the ability of public health professionals to discover environmental and occupational causes of disease, and to conduct exposure assessments needed to control workplace risks. The need for the development and application of new technology to conduct exposure assessments is widely recognized by many groups including NIOSH and the National Institute for Environmental Health Sciences (NIEHS). Advances in nanotechnology and materials sciences offer unique opportunities for the development of new air sampling sensor technologies based on organic electronic circuits. Field-effect transistors are the basic building blocks for electronic circuits, and organic field-effect transistors (OFETs) are those made with organic semiconductors (OSCs). OSCs are susceptible to non-covalent interactions, trapping and doping, photoexcitation, dimensional deformation, and other mild transformations. These transformations alter the electronic input- output characteristics of the semiconductors and these changes in input-output characteristics can be used to detect and quantify the chemical and physical stimuli that cause these electronic modifications. Thus, OSCs are a promising new platform for the construction of various types of sensors. The long-term goal of this research is to develop inexpensive, compact, sensitive and reliable gas/vapor sensors using organic materials technology. In this application, as a proof of concept, we propose to develop a sensor that will be able to detect low concentrations of ammonia for a variety of occupational and environmental applications. We will use a novel OFET-based technology to develop these sensors. These circuits have great promise for use as environmental sensors because they can be made from a variety of materials with specific chemical interactions with environmental agents. To-date this technology has not been applied to the development of air sampling sensors. While we initially plan to demonstrate this technology's ability to sense ammonia, the novelty of the technology could potentially extend to any gas-phase or solution-phase sensing scheme. To accomplish our goal, we propose 4 specific aims: In Specific Aim 1 we will investigate a range of organic materials that can be incorporated into OFET sensors for their response to ammonia. We will select the optimal materials and develop the printed circuit sensors for further testing. In Specific Aim 2 we will integrate multiple sensitive OFETs developed in Aim 1 into higher order circuits for synergistic responses, potentially increasing sensitivity and specificity to ammonia, and ultimately other nitrogen containing compounds (e.g. aromatic amines, nicotine). In Specific Aim 3 we will conduct laboratory testing of the OFET samplers developed in Aims 1 and 2 using a small bench scale apparatus and Specific Aim 4 will consist of a field validation of the samplers. If successful, this exploratory research project will result in the first application of OFET-based technology to air sampling.